Advanced Production Systems for Fresh Citrus in Florida

Fresh citrus fruit production in the state of Florida has been limited in recent years due to the effects of huanglongbing (HLB) disease. The causal pathogen of HLB, Candidatus Liberibacter asiaticus, is vectored by the Asian citrus psyllid (ACP, Diaphorina citri). Affected citrus trees display chlorotic leaves and limbs, and fruit is usually discolored, misshapen, and otherwise of sub-standard quality. In November, 2013, a series of trials were initiated at the University of Florida, Indian River Research and Education Center in Fort Pierce. These trials are evaluating different, new production scenarios for fresh citrus (focusing on ‘Ray Ruby’ grapefruit and ‘Valencia’ orange) in the age of HLB in Florida. Production elements of interest are high-density tree planting (i.e. greater than 400 trees/acre), drip liquid-fertigation, and weather-sensor guided irrigation scheduling. Collectively, these elements of interest are referred to as “Advanced Production Systems” (APS) and are being compared to control plots of grapefruit and orange planted according to conventional methods (i.e. less than 200 trees/acre and using dry, granular fertilizer). It is expected that the APS tree blocks will come into profitable bearing earlier than blocks planted at conventional standards, and that this accelerated fruit production will help offset the negative pressure of HLB. Included in these trials are protected culture grapefruit plantings that are evaluating the feasibility of producing fresh fruit in enclosed structures. These structures were made with screen cloth that physically separates the tree and the ACP insect vector. In this respect, HLB development should be prevented in grapefruit trees planted within these enclosures, relative to open-air grapefruit plantings. The system of covered fruit production is referred to as “Citrus Undercover Production Systems” (CUPS) and has ‘Ray Ruby’ grapefruit planted at super-high densities (i.e. greater than 800 trees/acre) with drip liquid-fertigation. These trials are on-going; however, their progress-to-date, with regards to tree-growth, will be reported and discussed.